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ClanLib 2D API - Overview - Part 2

Creating a display window

Lets make this overview a little bit less dry, and put in some code.

	// Init modules
	CL_SetupCore::init();
	CL_SetupDisplay::init();
	CL_SetupGL::init();

	// Create a window
	CL_DisplayWindow window("My first window", 640, 480);

	// Insert your code here
	CL_Display::clear();

	// Deinit modules
	CL_SetupGL::deinit();
	CL_SetupDisplay::deinit();
	CL_SetupCore::deinit();

First, we initialize the components we need. Note that we use SetupGL::init(), to use OpenGL to display our graphics. Currently OpenGL is the only supported display target in ClanLib 0.7. DirectX7, DirectX8, XLib targets are under development.

We then create a displaywindow using CL_DisplayWindow with the size 640x480. Afterwards we clear the display using CL_Display::clear().

ClanDisplay has support for multiple displaywindows. You can switch between them, make any of them fullscreen / windowed, close them or create any new ones.

	// Create two windows
	CL_DisplayWindow window1("My first window", 320, 200);
	CL_DisplayWindow window2("My second window", 800, 600);

	window1.get-gc()->clear();
	window2.get-gc()->clear();

Note that we call the clear() function a bit differently than in our previous example. Now we are using objects directly without calling the static function CL_Display::clear().

Using the display component

There are two ways to operate the display component in ClanLib, either using static functions (like in ClanLib 0.6), or through objects (i.e. CL_GraphicContext or CL_DisplayWindow).

The static approach

Using static functions in CL_Display always works on the current active displaywindow and graphiccontext, so you don't have to get a pointer to a CL_DisplayWindow or CL_GraphicContext. The static functions in CL_Display (and any other class in ClanLib that uses static functions) is actually just routing calls to the currently selected objects.

To set the currently selected displaywindow, use:

CL_Display::set_current_window(CL_DisplayWindow *window)

Note that the last created window is always set to default, so unless you are using more than one displaywindow, you don't have to think about this.

Example of use:

int width = CL_Display::get_width();
int height = CL_Display::get_height();

CL_Display::clear(CL_Color::white);
CL_Display::draw_line(0, 0, width, height, CL_Color(255, 0, 0));

CL_Display::flip();

The object approach

The second approach is to explicitly specify which object you want to call your function on. There are mainly two objects you will use, CL_DisplayWindow and CL_GraphicContext.

To get a displaywindow object, you can either use CL_Display::get_current_window() to retrieve the current selected displaywindow, or store the displaywindows pointers as you create them.

To get the graphiccontext of a displaywindow, you call the get_gc() method on your displaywindow.

Example of use:

CL_DisplayWindow *window = CL_Display::get_current_window();
CL_GraphicContext *gc = window->get_gc();

int width = window->get_width();
int height = window->get_height();

gc->clear(CL_Color(255, 255, 255));
gc->draw_line(0, 0, 100, 100, CL_Color::red);

window->flip();

Move on to part three.